NASA's Curiosity rover has detected a strange burst of methane gas in the atmosphere on Mars, along with other organic chemicals in rocks on the planet's surface. The findings are raising new questions about the planet's habitability--today as well as in the past.
"That we detect methane in the atmosphere on Mars is not an argument that we have found evidence of life on Mars, but it is one of the few hypotheses that we can propose that we must consider as we go forward in the future," Dr. John Grotzinger, Curiosity project scientist at the California Institute of Technology in Pasadena, said on Dec. 16 in a news briefing at the American Geophysical Union's convention in San Francisco.
Using its onboard Sample Analysis at Mars (SAM) laboratory, the rover "sniffed" more than a dozen samples of the Martian atmosphere over a 20-month period. Grotzinger and his team found that methane levels shot up tenfold to an average of seven parts per billion over two months in late 2013 and early 2014, according to NASA.
The researchers aren't sure what caused the burst, but they've offered two potential explanations: an interaction between water and rocks called serpentization, or methane-belching microbes. Anaerobic bacteria produce around 95 percent of the methane on Earth.
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This image illustrates possible ways methane might be added to Mars' atmosphere (sources) and removed from the atmosphere (sinks). NASA's Curiosity Mars rover has detected fluctuations in methane concentration in the atmosphere, implying both types of activity occur on modern Mars.
Curiosity found other organic (carbon-containing) molecules in powder collected from drilling into an ancient rock called Cumberland.
The researchers say this is the first definitive evidence of organics found on the surface of Mars. While the presence of organics doesn't prove that life existed on ancient Mars, it suggests the planet may have had the ingredients required for life, the New York Times reported.
"Organics, large organic molecules, present in ancient rocks on Mars is also not an argument that there was once life on ancient Mars, Grotzinger added during the briefing, "but it is the kind of material that you would look for if life ever originated on Mars."
A paper describing the detection of methane was published online on Dec. 16 in the journal Science.